Well, sorry! I can't input Chinese characters at this moment.
Despite you are experienced Linux user, if you are new to LFS, I strongly recommend you go through the LFS handbook thoroughly before you proceed. You can find most answers from the book.
Most software can be upgraded seamlessly, except glibc. This one is rather tricky.
I suggest you build your system with a more recent version, say 6.4 or 6.5.